Element: beforeinput event

The DOM beforeinput event fires when the value of an <input> or <textarea> element is about to be modified. But in contrast to the input event, it does not fire on the <select> element. The event also applies to elements with contenteditable enabled, and to any element when designMode is turned on.

This allows web apps to override text edit behavior before the browser modifies the DOM tree, and provides more control over input events to improve performance.

In the case of contenteditable and designMode, the event target is the editing host. If these properties apply to multiple elements, the editing host is the nearest ancestor element whose parent isn't editable.

Note: Not every user modification results in beforeinput firing. Also the event may fire but be non-cancelable. This may happen when the modification is done by autocomplete, by accepting a correction from a spell checker, by password manager autofill, by IME, or in other ways. The details vary by browser and OS. To override the edit behavior in all situations, the code needs to handle the input event and possibly revert any modifications that were not handled by the beforeinput handler. See bugs 1673558 and 1763669.

Syntax

Use the event name in methods like addEventListener(), or set an event handler property.

addEventListener("beforeinput", (event) => {});

onbeforeinput = (event) => {};

Event type

An InputEvent. Inherits from UIEvent.

Event properties

This interface inherits properties from its parents, UIEvent and Event.

InputEvent.data Read only: Returns a string with the inserted characters. This may be an empty string if the change doesn't insert text (for example, when deleting characters).
InputEvent.dataTransfer Read only: Returns a DataTransfer object containing information about richtext or plaintext data being added to or removed from editable content.
InputEvent.inputType Read only: Returns the type of change for editable content such as, for example, inserting, deleting, or formatting text.
InputEvent.isComposing Read only: Returns a Boolean value indicating if the event is fired after compositionstart and before compositionend.

Examples

Feature Detection

The following function returns true if beforeinput, and thus getTargetRanges, is supported.

function isBeforeInputEventAvailable() {
  return (
    window.InputEvent &&
    typeof InputEvent.prototype.getTargetRanges === "function"
  );
}

Simple logger

This example logs the current value of the element, immediately before replacing that value with the new one applied to the <input> element.

HTML

html

<input placeholder="Enter some text" name="name" />
<p id="values"></p>

JavaScript

const input = document.querySelector("input");
const log = document.getElementById("values");

input.addEventListener("beforeinput", updateValue);

function updateValue(e) {
  log.textContent = e.target.value;
}

Result

Specifications

Specification
UI Events # event-type-beforeinput

Browser compatibility

BCD tables only load in the browser